Multi-speed magnetic recording playback

ABSTRACT

A magnetic recording playback system compatible with both an 8 mm video format and a rotary head digital audio tape form. A rotary head records tilted tracks on the tape. Each track is divided into four areas which are recorded with different types of audio signals. The signals may also be divided between adjacent tracks. Each area has its own control information. Different sampling rates are used for the two different formats.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic recording playback such as a videotape recorder for recording and playing back information using rotarymagnetic heads.

2. Background Art

Recently, so-called 8 mm video tape recorders have been standarized andput on the market. In a 8 mm video tape recorder of that sort, therotational diameter of a rotary magnetic head (the diameter of a rotarydrum) is set at 40 mm and an angle at which a magnetic tape is wound onthe rotary drum is set at 221 degrees. Video signals are recorded in aportion corresponding to the 180-degree winding angle, whereas PCM(pulse code modulation) audio signals are recorded in a portioncorresponding to the 36-degree winding angle. The portion correspondingto the remaining 5-degree winding angle is left as a surplus area. Theportion corresponding to the 36-degree winding angle is further dividedinto a portion a for use in recording clock signals, a portion b for usein recording data such as the PCM audio signals, a margin c forafter-recording, and a video overlap for use in continuously recordingvideo signals of the immediately preceding field. Moreover, trackingpilot signals f₁, f₂, f₃, f₄ are sequentially recorded in the wholeportion corresponding to the 221-degree winding angle on a track bytrack basis. These pilot signals f₁, f₂, f₃, f₄ are treated as signalsat frequencies of f_(H) /58, f_(H) /50, f_(H) /36, f_(H) /40, wheref_(H) is the horizontal synchronizing signal. A tracking error signal isformed from stroke components derived from the tracks on the left andright of the pilot signals continuously recorded on each track. Thenumber of revolutions of the rotary magnetic head is set at 1,800 rpm inthe NTSC system and 1,500 rpm in the PAL system since it is operated soas to record video signals. Furthermore, a plurality of portions (fiveportions) corresponding to the 36-degree winding angle are formed in theportion corresponding to the 180-degree winding angle so that only audiosignals may be recorded therein.

The audio signal recorded in the 36-degree portion is so arranged as tohave a sampling frequency of 2 f_(H) (roughly 31.5 kHz), 10 quantizingbits, and 2 channels. However, the 10-bit data is converted (compressed)into an 8-bit data before being recorded on the magnetic tape.

On the other hand, the R-DAT (rotational head digital audio tape) systemhas recently been standardized in order to record and play backhigh-definition audio signals. The R-DAT has adopted a standardcomprising a magnetic tape winding angle of 90 degrees, a rotary drumdiameter of 30 mm, a sampling frequency of 48 kHz. 44.1 kHz or 32 kHz,16 quantizing bits, and 2 channels.

The track corresponding to a 90-degree winding angle is, as shown inFIG. 4, divided into 16 portions and data shown in Table 1 is recordedin each portion. In this case, one block is composed of 288-bit data andthe 8-bit data is converted (modulated) into 10-bit data before beingrecorded on the magnetic tape.

The frequency f_(ch) represents a clock signal of 9.408 MHz.

As shown in Table 1, the data comprises (1) a subcode signal recordingportion consisting of 2, 3, 4, (2) a tracking signal recording portionof 5, 6, 7, (3) a PCM audio signal recording portion of 8, 9, (4) atracking signal recording portion of 10, 11, 12 and (5) a subcoderecording portion of 13, 14, 15.

                  TABLE 1                                                         ______________________________________                                                                  Number   Frequency                                                   Angle    of       (micro-                                              Signal (degree) blocks   seconds)                                   ______________________________________                                         1 MARGIN   1/2    f.sub.ch                                                                            5.051  11     420.9                                   2 PLL      1/2    f.sub.ch                                                                            0.918  2       76.5                                   3 SUB-1                 3.673  8      306.1                                   4 POST AMBLE                                                                             1/2    f.sub.ch                                                                            0.459  1       38.3                                   5 IBG      1/6    f.sub.ch                                                                            1.378  3      114.8                                   6 ATF                   2.296  5      191.3                                   7 IBG      1/6    f.sub.ch                                                                            1.378  3      114.8                                   8 PLL (PCM)                                                                              1/2    f.sub.ch                                                                            0.918  2       76.5                                   9 PCM                   58.776 128    4898.0                                 10 IBG      1/6    f.sub.ch                                                                            1.378  3      114.8                                  11 ATF                   2.296  5      191.3                                  12 IBG      1/6    f.sub.ch                                                                            1.378  3      114.8                                  13 PLL (SUB)                                                                              1/2    f.sub.ch                                                                            0.918  2       76.5                                  14 SUB-2                 3.673  8      306.1                                  15 POST AMBLE                                                                             1/2    f.sub.ch                                                                            0.459  1       38.3                                  16 MARGIN   1/2    f.sub.ch                                                                            5.051  11     420.9                                  TOTAL                    90.000 196    7500.0                                 ______________________________________                                    

There are two systems for recording and playing back digital audiosignals on a magnetic tape using a rotary magnetic head. However, sincethe 8 mm video tape recorder is mainly designed to record video signals,its audio signal sampling frequency is low besides the sound quality isinferior to what is offered by the R-DAT. On the other hand, the R-DATis disadvantageous in that it is incapable of recording and playing backvideo signals but can only play back audio signals.

There are two systems for recording and playing back digital audiosignals on a magnetic tape using a rotary magnetic head. However, thesound quality is determined by the sampling frequency. The low samplingfrequency device has failed to realize what is accomplished by the highsampling frequency device. Also, since the 8 mm video tape recorder ismainly designed to record video signals, its audio signal samplingfrequency is low and besides the sound quality is inferior to what isoffered by the R-DAT. In addition to the above disadvantage, the problemis that a 4-channel audio signal cannot be efficiently recorded andplayed back.

SUMMARY OF THE INVENTION

An object of this invention is to provide a rotary-head magneticrecording playback compatible with both 8 mm video tape recording andR-DAT recording.

The magnetic recording playback of the invention is characterized inthat a track is formed by rotary magnetic heads in such a manner as tobe tilted in the longitudinal direction of a magnetic tape. The track isdivided into a plurality of areas and analog signals are sampled at aclock rate of substantially a frequency Nf and data are sampled everyNth clock pulses from the corresponding area as a group. Accordingly,the magnetic playback operates with higher frequency clocks which allowsnot only the enjoyment of high quality audio signals but also theplayback of the recorded signals is operated with lower frequency clocksby means of such a device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a magnetic recording playback embodying thepresent invention.

FIG. 2 is a typical plan view of the track therein.

FIG. 3 is a typical plan view of the areas.

FIG. 4 is a typical plan view of the track in a conventional magneticrecording playback.

FIGS. 5, 8(a), 8(b) and 8(c) are typical waveform charts showing thesampling states according to the present invention.

FIGS. 6 and 7 are block diagrams of the PCM encoders thereof.

FIGS. 9 and 10 are block diagrams of the PCM decoders thereof. FIG. 11is a typical waveform chart of the output signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of a magnetic recording playback (8 mm videotape recorder) embodying the present invention. As shown in FIG. 1, tworotary magnetic heads 1 are attached to a rotary drum (not shown) atpositions 180 degrees apart from each other. A signal is alternatelysupplied from a recording amplifier 4 to the rotary magnetic heads 1through switches 2 and 3, whereas signals are respectively supplied fromthe rotary magnetic heads 1 to a playback amplifier 5 through theswitches 2 and 3. Signals are respectively supplied from a videomodulator 8 and a PCM encoder 9 to the recording amplifier 4 through aswitch 6 and a pilot signal produced by a pilot signal generator 35 isalso supplied thereto. A signal from the playback amplifier 5 issupplied to a video demodulator 10 and a PCM decoder 11 through a switch7. A PCM decoder 12 and a PCM encoder 13 correspond to the formats ofthe R-DAT and the signal from the playback amplifier 5 is supplied tothe PCM decoder 12 through the switch 7, whereas the output of the PCMencoder 13 is supplied to the recording amplifier 4 through the switch6. An oscillator 14 produces a clock signal f'_(ch), which is suppliedto the PCM encoder 13.

A motor 15 used to rotate the rotary drum is equipped with a frequencygenerator 16 and a pulse generator 17, and is driven by a drivingcircuit 18. The output of the frequency generator 16 is supplied to afrequency control circuit 19 and compared with a fixed reference signalproduced by an oscillation circuit contained therein. The frequencycontrol circuit 19 produces an error signal. A phase control circuit 20receives, through a switch 21, either (1) a vertical synchronizingsignal contained in the recording video signal separated by asynchronizing separator circuit 22, (2) a reference signal produced byan oscillator 23, (3) a reference signal produced by the PCM decoder 12or (4) a reference signal produced by the PCM encoder 13. The phasecontrol circuit 20 compares a pulse produced by the pulse generator 17with the reference signal in terms of phase and produces a signalcorresponding to the error. The output of the frequency control circuit19 is added by an adder 24 to the output of the phase control circuit 20and the sum is supplied to the driving circuit 18.

A motor 25 is used to rotate a capstan (not shown) and is equipped witha frequency generator 26. The output of the frequency generator 26 issupplied to another frequency control circuit 27 and a divider circuit28. The frequency control circuit 27 compares a fixed reference signalproduced by a built-in oscillation circuit with the output of thefrequency generator 26 and supplies the divided output to another phasecontrol circuit 29. The second phase control circuit 29 compares thesignal from the switch 21 with the signal from the divider circuit 28and supplies the error signal to the adder 30 through a switch 34. Theadder 30 adds the output of the second frequency control circuit 27 tothat of the second phase control circuit 29 and supplies the sum to adriving circuit 31, which drives the motor 25 for the capstan. Atracking control circuit 32 separates and extracts a pilot signal f_(p)from the output of the playback amplifier 5 to form a tracking errorsignal and supplies the signal to the adder 30 through the switch 34. ACPU (Central Processing Unit) 33 such as a microcomputer controls eachcircuit, element and switch in combination with the main centralprocessing unit (not shown).

The operation of the magnetic recording playback will now be described.On receiving instructions as to recording a normal video signal and anaccompanying PCM audio signal, the CPU 33 sends a control signal to thefrequency control circuits 19 and 27, the driving circuits 18 and 31 andso on, causing the motor 15 to rotate the rotary drum at its normalspeed (1,800 rpm and 1,500 rpm in the cases of the NTSC and PAL systems,respectively) and causing the motor 25 to rotate the capstan so that thespeed of the magnetic tape (not shown) may be set at the normal level.At this time, the frequency control circuit 19 effects servo control soas to make the frequency of the signal produced by the frequencygenerator 16 equal to that of the contained reference signal. Moreover,the switch 21 is operated so as to choose the output of thesynchronizing separator circuit 22, whereby the rotary drum is rotatedin such a manner as to be synchronized with the phase of the horizontalsynchronizing signal in the video signal to be recorded. The phasecontrol circuit 20 generates a head switching pulse (HSWP) for theswitches 2 and 3 as a reference for switching the two rotary magneticheads and supplies the pulse to each circuit.

The frequency control circuit 27 and the phase control circuit 29 placethe motor 25 under frequency and phase servo control. The second phasecontrol circuit 29 supplies an error signal to the adder 30 through theswitch 34 with the output of the synchronizing separator circuit 22 atthe output of the switch 21 being used as a reference. The error signalrepresents the difference between the output of the synchronizingseparator circuit 22 and that of the divider circuit 28. Consequently,the speed of the magnetic tape is so controlled as to remain at a fixedlevel (14.345 mm/s and 20.051 mm/s in the NTSC and PAL systems,respectively).

The video signal to be thus recorded is supplied to the video modulator8 for frequency modulation. Moreover, the audio signal to be recorded issupplied to the PCM encoder 9 and converted into a digital value (PCM).These signals are supplied to the recording amplifier 4 through theswitch 6 and then to the rotary magnetic heads 1 through the switches 2and 3 and are recorded on the magnetic tape. With the head switchingpulse generated by the phase control circuit 20 as a reference, thevideo signal and the audio signal are recorded in the 180-degree videosignal recording portion and the 36-degree audio signal recordingportion, respectively. Moreover, the tracking pilot signal generated bythe pilot signal generator 35 is superposed in terms of frequency on thevideo signal and on the PCM audio signal and recorded therewith. Thethen used pilot frequency may be made identical with the pilot signal inthe PAL system. It is thus facilitated to separate the clock signalf'_(ch) from the pilot signal.

When the video signal is played back, the output signal (whichcorresponds to the vertical synchronizing signal) of the oscillator 23is supplied through the switch 21 to the phase control circuit 20 as areference signal. The switch 34 is then placed on the tracking controlcircuit 32 side and the motor 25 is also placed under the phase servocontrol corresponding to the tracking error signal resulting from thecrosstalk component of the pilot signals recorded on the adjoining leftand right tracks. The playback signals from the rotary magnetic heads 1are supplied to the video demodulator 10 and the PCM decoder 11 theswitch 17. Accordingly, the video signal recorded in the 180-degreevideo signal recording portion and the audio signal recorded in the36-degree audio signal recording portion are demodulated and sent out.

When only a high-fidelity audio signal is to be recorded, the audiosignal is supplied to the PCM encoder 13 and converted into a digitalvalue. A PCM encoder similar to what is employed for the so-called R-DATmay be used as the PCM encoder 13. However, the PCM encoder 13 iscontrolled with a clock and timing different from those applied to theR-DAT.

In other words, one tilted track corresponding in length to the221-degree winding angle is divided into four areas, each having alength of 54 degrees as shown in FIG. 2, whereas 2.044-degree and2.956-degree excess portions are provided on the left and right,respectively. The four 54-degree areas A through D are further dividedinto nine portions and data shown in Table 2 are recorded in eachportion.

                  TABLE 2                                                         ______________________________________                                                       Angle    Number   Frequency                                             Signal                                                                              (degree) of blocks                                                                              (microseconds)                               ______________________________________                                        1 MARGIN   1/2f'.sub.ch                                                                          2.956    8.8    246.268                                    2 PLL (SUB)                                                                              1/2f'.sub.ch                                                                          0.672    2      55.97                                      3 SUB-1            2.687    8      223.88                                     4 POST AMBLE                                                                             1/2f'.sub.ch                                                                          0.336    1      27.985                                     5 PLL (PCM)                                                                              1/2f'.sub.ch                                                                          0.672    2      55.97                                      6 PCM              42.985   128    3582.08                                    7 PLL (SUB)                                                                              1/2f'.sub.ch                                                                          0.672    2      55.97                                      8 SUB-2            2.687    8      223.88                                     9 POST AMBLE                                                                             1/2f'.sub.ch                                                                          0.336    1      27.985                                     TOTAL              54.0     160.8  4500.0                                     ______________________________________                                    

As is obvious from Table 1, the format according to the presentinvention excludes the tracking data recording portions 5, 6, 7 and 10,11, 12 and the last margin 16 in Table 1. The clock f'_(ch) in this caseis set at e.g., 12.864 MHz (=160.8×288×(10/8)/0.0045). The combinationis needless to say alterable, provided that the 54-degree winding angleand 4500 microsecond recording time are held. For example, the PLL (PCM)clock recording portion having two blocks may be dispensed with and themargin may have 10.8 instead of 8.8 blocks. Moreover, the surpluses onboth sides may be made optional.

It thus becomes possible to record and play back information only byaltering the timing but not the coding of the format of the alreadystandardized R-DAT.

The audio signal applied to the PCM encoder 13 is converted into adigital value corresponding to the clock signal f'_(ch) supplied by theoscillator 14 and that timing is controlled by the CPU 33, so that theaudio signal is converted into the format signal shown in Table 2. Thatsignal is supplied to the rotary magnetic heads 1 through the switch 6,the recording amplifier 4, and the switches 2 and 3 and thus recorded onthe magnetic tape 1. With the head switching pulse supplied by the phasecontrol circuit 20 as a reference, an area pulse corresponding to atleast one of the areas A through D is formed and the signal is recordedin the area corresponding to the area pulse.

The frequency control circuit 29 and the driving circuit 18 are socontrolled by the CPU 33 as to make the rotary drum rotate at a speed of2,000 rpm. Moreover, the switch 21 is caused to supply a signalsynchronous with the clock f'_(ch) produced by the PCM encoder 13. Theclock synchronous signal is supplied to the phase control circuit 20 asa reference signal. The frequency control circuit 27 and the drivingcircuit 31 are controlled likewise and the speed of the magnetic tape isset at 10.025 mm/s, which is half of the standard speed 20.051 mm/s inthe PAL system. The track pitch becomes 13.3 micrometers at that thusset speed. As a result, the width of the rotary magnetic head forstandard or one-half speed use in either the NTSC or the PAL systemcomes within the range of audio and pilot signal recording playback andtracking control by means of the cross-talk component of the pilotsignal, thus making it unnecessary to use a rotary magnetic head havinga specially arranged width.

When the audio signal thus recorded is played back, the signal from therotary magnetic head 1 is supplied to the playback amplifier 5 throughthe switches 2 and 3 and then to the PCM decoder 12 through the switch7. The PCM decoder 12 is controlled by the CPU 33 and is used to extractthe clock signal f'_(ch) from the playback signal and to read out thedata in each portion with the clock signal f'_(ch) as a reference. Theaudio signal is converted into an analog signal and sent out. Thetracking pilot signal contained in the playback signal is supplied tothe tracking control circuit 32, whereby the tracking error signal isformed. The tracking error signal is supplied to the adder 30 throughthe switch 34 and used for tracking control. In other words, thetracking signals (ATF) are recorded in the R-DAT in the portionspreceding and following the PCM audio signal recording portion as shownin Table 1. The cross-talk component derived from those portions in theleft and right tracks are sampled and held at a given timing, so thatthe tracking error signal is formed from the differential signal. As inthe case of an ordinary 8 mm video tape recorder, however, thedifferential signal of the cross-talk components of the sequentiallyrecorded pilot signals from the left and right tracks is used to formthe tracking error signal.

                  TABLE 3                                                         ______________________________________                                        Area D      Re     Re.sub.2                                                                           Re.sub.4                                                                            Be   Be   Be.sub.4                                                                           Be.sub.4                                                                           Z                                       Lo     Lo.sub.2                                                                           Lo.sub.4                                                                            Fo   Fo   Fo.sub.4                                                                           Fo.sub.4                                                                           Y                                C      Re     Re.sub.2                                                                           Re.sub.4                                                                            Re   Be   Re.sub.4                                                                           Be.sub.4                                                                           X                                       Lo     Lo.sub.2                                                                           Lo.sub.4                                                                            Lo   Fo   Lo.sub.4                                                                           Fo.sub.4                                                                           W                                B      Re     Re.sub.2                                                                           Re.sub.4                                                                            Be   Re   Bo.sub.4                                                                           Re.sub.4                                                                           V                                       Lo     Lo.sub.2                                                                           Lo.sub.4                                                                            Fo   Lo   Fo.sub.4                                                                           Lo.sub.4                                                                           U                                A      Re     Re.sub.2                                                                           Re.sub.4                                                                            Re   Re   Re.sub.4                                                                           Re.sub.4                                                                           T                                       Lo     Lo.sub.2                                                                           Lo.sub.4                                                                            Lo   Lo   Lo.sub.4                                                                           Lo.sub.4                                                                           S                           Sampling                                                                              48     96     192   48   48   96   96   48                            frequency                                                                     No. of  2      2      2     4    4    4    4    8                             channels                                                                      No. of  4      2      1     2    2    1    1    1                             recording                                                                     times                                                                         ______________________________________                                    

The data to be recorded in each area A through D may be formed as shownin Table 3. Given that stereo audio signals L and R (left and right)constitute the recording data with a sampling frequency of 48 kHz andthat consecutive numbers are given to the fixed number of data (words)respectively sampled at the clock rate, the odd number left signal (Lo)and the even number right signal (Re) are recorded in the area A,whereas the odd number right signal (Ro) and the even number left signal(Le) are recorded in the area A in the adjoining tracks. That is, thedata is interleaved in two tracks as well as being interleaved in eachtrack. Complete data can thus be played back by obtaining the signalsfrom the two tracks. Although there are advantages to using an encoderand a decoder similar to R-DAT encoders and decoders, different ones maybe used, which would permit any type of interleaving. As recording islikewise carried out in each of the areas B, C, D, it is possible torecord the two channel (L, R) data on one tilted track four times. InTable 3, only the data Lo and Re are listed for convenience, as will bethe practice hereafter.

Assuming the sampling frequency is 96 kHz, which is twice as high as thereference frequency of 48 kHz, the data is divided into the even numbersignals Le and Re and the odd number signals Lo and Ro. Then a new orderis applied to the even number signals Le and Re and, in the new order,the same division as in the above case is made. In other words, the oddnumber signal Lo₂ in the new order and the even number signal Re₂ arerecorded in the area A, whereas the odd number signal Ro₂ in the neworder the even number signal Le₂ are recorded in the adjoining area A.Although a new order is also given to the odd number signals Lo and Roin the original order and the same process is carried out for them,these signals are recorded in the area B. The resulting signal recordedin each area is substantially the same as what is sampled at 48 kHz and,when it is decoded at the clock rate of 48 kHz, the same audio signal aswhat had been sampled at 48 kHz can be played back. By this is meantthat, if, for example, one sampling data is divided into high and loworder bits and respectively recorded in different areas, the abovedescription will become unjustifiable.

Assuming that the sampling frequency is four times as high as thereference frequency, namely 192 kHz, the data is divided into groups ona four sample basis. As shown in FIG. 5, for instance, sampling valuesL₁₁, R₁₁ at time t₁₁ and sampling values L₂₁, R₂₁ four clock pulseslater, and sampling values L₃₁, R₃₁ four clock pulses still later aretreated as one group. In the same manner, sampling values L₁₂, R₁₂, L₂₂,R₂₂, L₃₂, R₃₂ are treated as a second group; sampling values L₁₃, R₁₃,L₂₃, R₂₃, L₃₃, R₃₃ as a third group and sampling values L₁₄, R₁₄, L₂₄,R₂₄, L₃₄, R₃₄ as a fourth group. Then the same process as describedabove is carried out so as to record the four groups in the differentareas A through D, respectively. New order is given to the first groupso that the odd number signal Lo₄ and the even number signal Re₄ arerecorded in the area A; and the odd number signal Ro₄ and the evennumber signal Le₄ are recorded in the following area A. In this case,the signal to be recorded in area also becomes substantially equivalentto what is sampled at the clock rate of the reference frequency. Therebyit becomes possible to play back using a decoder at the referencefrequency.

If the data is divided into groups on a two sample basis in the samemanner, playback using a decoder of a frequency twice as high as thereference frequency becomes possible.

Accordingly, it is obviously preferred that the recording areacorrespond to a case of lower sampling frequency.

A description will subsequently be given of a case where a 4-channelaudio signal is recorded by adding the right and left stereo audiosignals (L and R) to, e.g., the front and back audio signals (F and B).In this case, assuming the sampling frequency is the reference frequencyof 48 kHz, the left and right stereo signals (L and R) and thecorresponding front and back signals (F and B) are recorded in order inthe areas A and B, respectively. In principle, the left and right audiosignals (L and R) and the front and back audio signals (F and B) may berecorded in one area. However, such simultaneous recording isdisadvantageous in a recorder capable of playing back only 2-channelstereo signals (left and right signals (L and R)) because the front andback audio signals recorded in same area cannot be played back.Therefore, the left and right signals (L and R) and the front and backsignals (F and B) should preferably be recorded in different respectiveareas. The left and right signals (L and R) or the front and backsignals (F and B) may be recorded in either area. For example, the leftand right signals (L and R) may also be recorded in the areas B and Aand the front and back signals (F and B) in the areas C and D. In thiscase, the left and right signals (L and R) and the front and backsignals (F and B) may also be recorded in the areas C and D, so thatinformation is recorded on one tilted track twice. In the above case,the odd number signal Lo (Fo) and the even number signal Re (Be) arerecorded in each area first and the odd number signal Ro (Bo) and theeven number signal Le (Fe) are subsequently recorded in the adjoiningarea. The area in which the left and right sigals L and R and the frontand back signals F and B are recorded can be determined freely. However,the area in which the left and right signals L and R are recorded shouldpreferably correspond to the area in which the 2-channel stereo signalsL and R at the sampling frequency of 48 kHz are first recorded or inwhich the 2-channel stereo signals L and R at the sampling frequency of96 kHz are either first or subsequently recorded.

When the 4-channel audio signal is sampled at 96 kHz, which is twice ashigh as the reference frequency, it is first divided into odd numbersampling values Lo, Ro, Fo and Bo and even number sampling values Le,Re, Fe and Be. Then a new order is respectively given to the odd numbersignals Lo, Ro, Fo and Bo and to the even number signals Le, Re, Fe andBe. Of the odd number left and right signals Lo and Ro, the signal Lo₄and the even number signal Re₄ in the new order are recorded in the areaA. Of the odd number signals Lo and Ro, the odd number signal Ro₄ andthe even number signal Le₄ in the new order are recorded into thesubsequent area A. Of the odd number front and back Fo and Bo, the oddnumber signal Fo₄ and the even number signal Be₄ in the new order arerecorded in the area B and, of the even number signals Fo and Bo, theodd number signal Bo₄ and the even number signal Fe₄ in the new orderare recorded in the subsequent area B. The even number signals Le, Re,Fe, Be are likewise recorded in the areas C and D. In this case, thearea in which the left and right signals and the front and back signalsare recorded may also be optionally determined. However, such an optionshould preferably correspond to the cases of 2-channel stereo recordingat the reference frequency and 4-channel recording at the referencefrequency. That is, the left and right signals L and R sampled at 96 kHzshould be recorded in the same area as that where, for example, the leftand right signals sampled at 48 kHz should be recorded, whereas thefront and back signals F and B sampled at 96 kHz should be recorded inthe same area as that where the front and back signals sampled at 48 kHzshould be recorded. In so doing, even a recorder having the 48 kHzsampling clock is able to play back a tape recorded with a signal havingthe 96 kHz sampling rate. In this case, data is recorded in one tiltedtrack once.

Assuming the recording data consists of data S through Z which areindependent from each other, 8-channel data can obviously be recordedwith 48 kHz sampling.

When the recording wavelength must be made longer, the areas A and B andthe areas C and D should each be treated as one area.

As set forth above, the areas A through D have been assumed equivalent.When the two rotary magnetic heads positioned 180-degrees apart fromeach other are actually used to record and play back data, however, bothof them contact the magnetic tape in the area A or D. If one of therotary heads is used to play back data with the other being used torecord data (e.g., for after recording), the data on one side overlapsthe one on the other. The increased noise may make it difficult tocorrectly effect recording playback. When one of the rotary heads isused to play back data with the other being used for recording data, thedata in the area B or C which is centrally located should be played backand data should be recorded in the area A or D. When the 4-channel audiosignal is recorded at, for example, the reference frequency samplingrate, the left and right signals L and R and the front and back signalsF and B should preferably be recorded in the first rotation with, forexample, the areas A and D (or B and C) being paired and the left andright signals L and R and the front and back signals F and B should berecorded in the second rotation with the areas B and C (or A and D)being paired.

When the same arrangement as that in the case of the R-DAT is used,16-bit, 2-channel left and right audio signals are recorded incombination on one track in each of the areas A through D. If the traveldirection of the magnetic tape is inverted on an area basis with theareas A and C for use in recording playback in the case of forwardtransport and, hence, the areas B and D in the case of backwardtransport, continuous recording playback from the track in each of thefour areas will become possible.

Recording playback with the left and right channels being independent ofeach other is also possible, provided that the areas A and C are usedfor the left channel and the areas B and D for the right channel.

If the upper and lower order 8-bit data or left and right channel datais played back on an area basis at the twofold sampling frequency rate(96 kHz), a higher-fidelity audio signal can be played back.Furthermore, 4-bit data may be played back from each area at a fourfoldsampling frequency. Moreover, 4-channel, 6-channel or 8-channelrecording playback are also possible with two, three or four areasrespectively being used in combination.

Now, an embodiment of the PCM encoder 13 will be described. As shown inFIG. 6, the PCM encoder 13 may be composed of an A/D converter 41 and amemory 42. The A/D converter 41 converts the received analog left andright signals L and R into digital signals in accordance with a clock ata fixed frequency (96 kHz according to the embodiment) and causes thememory 42 to store the signals. The signals stored in the memory 42 areread out in accordance with the clock of the same frequency. Thesampling frequency of the data recorded in each area will become 48 kHzif the data read out with the odd number clock is recorded in the area Aand what is read out with the even number clock in the area B.

The same effect is accomplished according to an embodiment shown in FIG.7. In this embodiment, two systems of respective A/D converters 41A and41B and memories 42A and 42B are actuated by the clock signal at 48 kHz.The clock signal (FIG. 8(b)) at 48 kHz supplied to the A/D converter 14Aand the memories 42A is delayed 180-degrees in phase by a delay circuit43 but is directly supplied to the A/D converter 41A and the memories42A (FIG. 8(c)). Consequently, e.g., a given analog signal (FIG. 8(c))is sampled by sampling pulses at 48 kHz, each lagging the other by aphase difference of 180 degrees, and the sampled values are respectivelyrecorded in areas A and B. The original signal becomes practicallyequivalent to what is sampled at frequency of 96 kHz.

FIG. 9 shows an embodiment of the PCM decoder for decoding such asignal. In this embodiment, the playback signals (the signals sampled bythe 48 kHz clock signals 180-degrees out of phase with each other) fromthe areas A and B are added in an adder 51 to practically become thesignal sampled at 96 kHz before being supplied to a D/A converter 52. Inthe D/A converter 52 supplied with the 96 kHz clock signal, the digitalsignal read out in accordance with the clock is smoothed by a low-passfilter 53 and then sent out as an analog signal.

FIG. 10 shows another embodiment of the PCM decoder 12. According tothis embodiment, there are two systems of respective D/A converters 52Aand 52B, each actuated by the 48 kHz clock. The outputs of the D/Aconverters 52A and 52B are supplied to a sample and hold circuit 54 andthe output therof is sent to the low-pass filter 53. The 48 kHz clocksupplied to the D/A converter 52A is 180-degrees delayed by a delaycircuit 55 but is directly supplied to the D/A converter 52B. Moreover,the undelayed clock and the 180-degrees delayed clock are supplied tothe sample and hold circuit 54 for the respective digitized signals. Thedigital playback signal from the area A is converted by the D/Aconverter 52A into an analog signal (shown by a solid line in FIG. 11),whereas the digital playback signal from the area B is converted by theD/A converter 52B into an analog signal (shown by a broken line in FIG.11). These converted analog signals are supplied to the sample and holdcircuit 54. The sample and hold circuit 54 successively holds, forexample, the levels of a₁, a₂, a₃ of the output of the D/A converter 52Awith the undelayed clock and also the levels b₁, b₂ of the output of theD/A converter 52B correspondingly to the delayed clock. The output thuscombined is smoothed by the low-pass filter 53, so that the originalsignal (shown by an alternately long and short dash line in FIG. 11) isplayed back.

The systems of encoders or decoders of 48 kHz thus provided makesubstantially possible the playback of the sampling signal of 96 kHzwithout providing a 96 kHz clock and its encoder or decoder. It is,needless to say, possible to play back the sampling signal of 48 kHz,provided that the signal thus encoded by the encoder and recorded in thearea A or B on an area basis is decoded by the 48 kHz decoder.

In the magnetic recording playback thus constructed according to thepresent invention, each track is formed in such a manner as to tilt inthe longitudinal direction of the magnetic tape and is divided into aplurality of areas. The analog signal is sampled at a clock rate ofsubstantially a frequency Nf. Data sampled every Nth clock pulses isrecorded as a group of data in the corresponding area so that ahigh-definition audio signal can be enjoyed using a recording playbackactuated with a higher frequency clock. In addition, the recordingsignal can be played back using a recording playback actuated with alower frequency clock.

In the magnetic recording playback of the present invention, a digitalsignal is recorded on and played back from a recording medium byconverting the analog signal to a digital signal. Two systems ofencoders or decoders are actuated with a clock of the same frequency.The clock phase driving one encoder or decoder and that driving theother encoder or decoder are put 180-degrees out of phase with eachother. Thereby a high-fidelity audio signal can be enjoyed using arecording playback actuated with a lower frequency clock.

In the magnetic recording playback according to the present invention,each track formed by the rotary magnetic head in such a manner as totilt in the longitudinal direction of the magnetic tape is divided intofour areas. The audio signal, composed of the left and right stereosignals and the other two signals, is sampled at the fixed frequencyclock to provide digital signals. The left and right digital signals arerecorded in at least one of the areas, whereas the other two digitalsignals are recorded in at least one of the remaining areas.Accordingly, in the 8 mm video tape recorder, high-definition 2-channeland 4-channel audio signal can be recorded on and played back from themagnetic tape without loss of efficiency and the magnetic tape processedby a recording playback capable of 4-channel signal recording andplayback becomes usable for playback by a recording playback of only2-channel signal recording and playback.

The magnetic recording playback is arranged according to the presentinvention so that each track is formed by the rotary magnetic head insuch a manner as to tilt in the longitudinal direction of the magnetictape. Each track is divided into a plurality of areas so that, when theanalog signal is sampled at the frequency 2f to provide the digitalsignal, the data sampled with the odd number clock are recorded as agroup in one of the areas and the data sampled with the even numberclock are recorded as a group in one of the remaining areas. Further,when the analog signal is sampled at the frequency f to provide thedigital signal, the data sampled at the freqency f are recorded as agroup in the area corresponding to what is used for recording the datasampled with the odd or even number frequency 2f clock. Accordingly, ahigh definition audio signal can be enjoyed using a recording playbackactuated with a higher frequency clock and the recorded signal can alsobe played back using a recording playback actuated with a lowerfrequency clock.

According to the present invention, in the magnetic recording playbackfor recording and playing back information by winding the magnetic tapeover 180-degrees on the rotary drum which has two rotary magnetic headspositioned 180-degrees apart from each other, each track is formed insuch a manner as to tilt in the longitudinal direction of the magnetictape and is divided into four areas. The analog signal is sampled withthe fixed frequency clock to provide the digital signal and when thedigital signal is recorded in an area, the two outer areas of the fourare treated as a pair, whereas the two inner areas thereof are treatedas a pair. Consequently, a higher-definition audio signal can be enjoyedusing the 8 mm video tape recorder and, when the signal played back byone of the rotary magnetic heads is recorded on the other (forafter-recording), accurate recording becomes possible because not onlynoise but also error can be minimized.

Also according to a generalization of the invention, in the magneticrecording playback for recording and playing back information by windingthe magnetic tape over 180-degrees on the rotary drum having two rotarymagnetic heads positioned 180-degrees apart from each other, each trackis formed in such a manner as to tilt in the longitudinal direction ofthe magnetic tape and is divided into a plurality of areas. The analogsignal is sampled with the fixed frequency clock to provide the digitalsignal, which is then recorded in an area. When the digital signalrecorded in one of the areas is played back and recorded in anotherarea, the playback of the signal recorded therein is started with theinnermost area and the recording thereof is started with the outermostarea. Consequently, a higher-definition audio signal can be enjoyedusing the 8 mm video tape recorder and, when the signal played back byone of the rotary magnetic heads is recorded on the other (forafter-recording), accurate recording becomes possible because not onlynoise but also errors can be minimized.

In the magnetic recording playback, each track is formed by the rotarymagnetic head rotated at a first speed in such a manner as to tilt inthe longitudinal direction of the magnetic tape. Each track is dividedinto first and second portions. At least the first portion is furtherdivided into the portion a for recording the clock signal, the portion bfor recording data such as the PCM audio signal, the margin c forafter-recording and the video overlap for continuously storing the videosignals in the immediately preceding field. The PCM audio or videosignal is recorded in the first or second portion byfrequency-superposing the tracking pilot signal thereon or is playedback from these portions. The track formed by the rotary magnetic headrotated at a speed higher than the first speed in such a manner as totilt in the longitudinal direction of the magnetic tape is also providedwith: a third portion for recording the first code signal; a fourthportion for recording the tracking control signal; a fifth portion forrecording the PCM audio signal; a sixth portion for recording thetracking control signal; a seventh portion for recording the second codesignal; an eighth portion for recording the third code signal which hasa number of blocks equal to those in the third portion corresponding tothe system for recording and playing back the data having the fixednumber of blocks in and from each of the third through seventh portions;a ninth portion for recording the PCM audio signal having a number ofblocks equal in number to the fifth portion; and a tenth portion forrecording the fourth code signal having blocks equal in number to theseventh portion. The rotation of rotary magnetic head is switched fromthe first to second speed. The tilted track composed of the first andsecond portions is divided into four areas. The data formed of theeighth, ninth and the tenth portions is recorded on and played back fromthe four areas. Accordingly, not only a video signal but also a highfidelity (Hi Fi) audio signal can be recorded and played back using theso-called 8 mm video tape recorder.

What is claimed:
 1. A magnetic recording playback, comprising:a rotarymagnetic head; a magnetic tape wound at an angle on said rotary magnetichead wherein said rotary magnetic head records on said tape tape trackstilted in a longitudinal direction of said tape; and means for switchinga rotation of said rotary magnetic head between a first speed and asecond speed; wherein each said track formed by said magnetic headrotating at said first speed comprises a first section and a secondsection and at least said first section comprises a first portion forrecording a clock signal, a second portion for recording a first digitalaudio signal, a third portion being a margin for after-recording and afourth portion being a video overlap for continuously recording videosignals in an immediately preceding field; wherein each said trackformed by said magnetic head rotating at said second speed higher thansaid first speed comprises a third section for recording a first codesignal, a fourth section for recording a tracking control signal, afifth section for recording a second digital audio signal, a sixthsection for recording a tracking control signal, a seventh section forrecording a second code signal, an eighth section for recording a thirdcode signal having blocks equal in number to a number of blocks in saidthird section corresponding to another system for recording and playingback data having a fixed number of blocks in and form said third throughseventh sections, a ninth section for recording blocks equal in numberto said fifth section and a tenth section for recording a fourth codesignal having blocks equal in number to said seventh section; andwherein each said track composed of said first and second sections isdivided into four areas; said playback further comprising: means forrecording or playing back said first digital audio signal in said firstsection nor said video signal in said third section byfrequency-superposing a tracking pilot signal on said first or secondsection respectively; and means for frequency-superposing first data ofsaid eighth, ninth and tenth sections on said pilot signal and recordingand playing back said first data in and from said four areas.
 2. Amagnetic playback as recited in claim 1, further comprising:means toregulate a travel speed of said magnetic tape to half of a referencespeed when said rotary head is rotating at said first speed; and a PALsystem for recording and playing back said video signal in and from saidfirst and second sections.
 3. A magnetic playback as recited in claim 1,further comprising sampling means for sampling an analog audio signal toproduce said first digital audio signal at a sample-rate twice as highas said second digital audio signal and wherein said recording meansrecords said first digital audio signal in only two of said areas.
 4. Amagnetic playback as recited in claim 2, further comprising samplingmeans for sampling an analog audio signal to produce said first digitalaudio signal at a sample-rate twice as high as said second digital audiosignal and wherein said recording means records said first digital audiosignal in only two of said areas.
 5. A magnetic playback as recited inclaim 1, further comprising sampling means for sampling an analog audiosignal to produce said first digital audio signal at a sampling ratefour times as high as said second audio signal and wherein saidrecording means records said first digital audio signal in all said fourareas.
 6. A magnetic playback as recited in claim 2, further comprisingsampling means for sampling an analog audio signal to produce said firstdigital audio signal at a sampling rate four times as high as saidsecond digital audio signal and wherein said recording means recordssaid first digital audio signal in all said four areas.
 7. A magneticplayback as recited in claim 1, wherein said analog audio signalcomprises left and right channel audio signals and wherein saidrecording means records digital left and right channel audio signals inone of said areas.
 8. A magnetic playback as recited in claim 2, whereinsaid analog audio signal comprises left and right channel audio signalsand wherein said recording means records digital left and right channelaudio signals in one of said areas.
 9. A magnetic playback as recited inclaim 3, wherein said analog audio signal comprises left and rightchannel audio signals and wherein said recording means records digitalleft and right channel audio signals in one of said areas.
 10. Amagnetic playback as recited in claim 5, wherein said analog audiosignal comprises left and right channel audio signals and wherein saidrecording means records digital left and right channel audio signals inone of said areas.
 11. A magnetic playback as recited in claim 2,wherein said pilot frequency has the same frequency as a pilot signalused by said recording or playing back means in recording said firstdigital audio signal and said video signal in and from said first andsecond sections through said PAL system.